Messages in this thread Patch in this message | | | Subject | Re: build failure in Linus' tree with gcc 4.4.3 | From | Matt Fleming <> | Date | Tue, 21 Feb 2012 11:32:13 +0000 |
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On Tue, 2012-02-21 at 21:38 +1100, Stephen Rothwell wrote: > Hi Matt, > > On Tue, 21 Feb 2012 10:01:57 +0000 Matt Fleming <matt.fleming@intel.com> wrote: > > > > Looks like the segfault is caused by an unaligned access? How does this > > patch look? > > I didn't try it, but it won't work. PowerPC is big endian, the data you > are copying is little endian ....
Urgh, you must feel like you're talking to a brick wall. I forgot you mentioned the endian issue in your original post, sorry. Let's try this one more time...
From b3885c72be4cb06b2647a5067432da6017ea7902 Mon Sep 17 00:00:00 2001 From: Matt Fleming <matt.fleming@intel.com> Date: Mon, 20 Feb 2012 17:32:42 +0000 Subject: [PATCH] x86, efi: Fix unaligned access and endian issues
We need to read from and write to 'buf' a byte at a time otherwise it's possible we'll perform an unaligned access, which can lead to a segfault when cross-building an x86 kernel on risc architectures.
Also, we may need to convert the endianness of the data we read from/write to buf, so let's add some helper functions to do that.
Stephen Rothwell noticed this bug when he hit a segfault while cross-building an x86_64 allmodconfig kernel on PowerPC.
Cc: H. Peter Anvin <hpa@zytor.com> Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Matt Fleming <matt.fleming@intel.com> --- arch/x86/boot/tools/build.c | 44 ++++++++++++++++++++++++++++++------------ 1 files changed, 31 insertions(+), 13 deletions(-)
diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c index 4e9bd6b..56efa6f 100644 --- a/arch/x86/boot/tools/build.c +++ b/arch/x86/boot/tools/build.c @@ -133,6 +133,26 @@ static void usage(void) die("Usage: build setup system [> image]"); } +static inline u32 read32_le(u8 *src) +{ + u32 data; + + data = *src++; + data |= *src++ >> 8; + data |= *src++ >> 16; + data |= *src++ >> 24; + + return data; +} + +static inline void write32_le(u8 *dst, u32 data) +{ + *dst++ = data; + *dst++ = data >> 8; + *dst++ = data >> 16; + *dst++ = data >> 24; +} + int main(int argc, char ** argv) { #ifdef CONFIG_EFI_STUB @@ -192,44 +212,42 @@ int main(int argc, char ** argv) /* Patch the setup code with the appropriate size parameters */ buf[0x1f1] = setup_sectors-1; - buf[0x1f4] = sys_size; - buf[0x1f5] = sys_size >> 8; - buf[0x1f6] = sys_size >> 16; - buf[0x1f7] = sys_size >> 24; + write32_le(&buf[0x1f4], sys_size); #ifdef CONFIG_EFI_STUB file_sz = sz + i + ((sys_size * 16) - sz); - pe_header = *(unsigned int *)&buf[0x3c]; + pe_header = read32_le(&buf[0x3c]); /* Size of code */ - *(unsigned int *)&buf[pe_header + 0x1c] = file_sz; + write32_le(&buf[pe_header + 0x1c], file_sz); /* Size of image */ - *(unsigned int *)&buf[pe_header + 0x50] = file_sz; + write32_le(&buf[pe_header + 0x50], file_sz); #ifdef CONFIG_X86_32 /* Address of entry point */ - *(unsigned int *)&buf[pe_header + 0x28] = i; + write32_le(&buf[pe_header + 0x28], i); /* .text size */ - *(unsigned int *)&buf[pe_header + 0xb0] = file_sz; + write32_le(&buf[pe_header + 0xb0], file_sz); /* .text size of initialised data */ - *(unsigned int *)&buf[pe_header + 0xb8] = file_sz; + write32_le(&buf[pe_header + 0xb8], file_sz); #else /* * Address of entry point. startup_32 is at the beginning and * the 64-bit entry point (startup_64) is always 512 bytes * after. */ - *(unsigned int *)&buf[pe_header + 0x28] = i + 512; + write32_le(&buf[pe_header + 0x28], i + 512); /* .text size */ - *(unsigned int *)&buf[pe_header + 0xc0] = file_sz; + write32_le(&buf[pe_header + 0xc0], file_sz); /* .text size of initialised data */ - *(unsigned int *)&buf[pe_header + 0xc8] = file_sz; + write32_le(&buf[pe_header + 0xc8], file_sz); + #endif /* CONFIG_X86_32 */ #endif /* CONFIG_EFI_STUB */ -- 1.7.4.4
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